Electrodeposition of lustrous nickel



United States Patent "ice 3,152,973 ELECTRODEPOSITION OF LUSTROUS NICKEL Thaddeus W. Tomaszewski, Dearbo'rn, and Henry Brown,

HuntingtonWoods, Mich., assignors, by mesne assignments, to The Udylite Corporation, Warren, M|ch., a corporation of Delaware 1 I r No Drawing. Filed. July 26, 1960, Ser. No. 45,287 19 Claims. (Cl. 204-41) obtain the most pleasing satinfinishes, dull nickel or dull chromium plate is most often employed, and is subsequently brush finished to obtain the satin lustre. This latter step is expensive, andalso decreases the COl'lOSlOIl protection afforded by the satin plate because the brush marks or polishing scratches penetrate appreciably in the plate especially in recessed areas where the plate is thin. For

these reasons, that is, expense, and decreased corrosion resistance, satin finished nickel or chromium are notusually used for exterior parts of 'automobilesor boats.

It is an object of this invention to provide plating baths and methods to produce fine-grained lustrous satin nickel directly from "the bath that not only has a very pleasing appearance, but which can be high-lighted by buffing raised areas to give beautiful two-tone elfects, and which will also provide exceptionally good corrosion protection tothe ba'sis metal such as ferrous, aluminum, magnesium, brass, copper and zinc articles. 7

It has now been found that nickel plating baths normal- 1y designated as bright nickel baths, or semi-bright nickel baths can be modified to plate a fine-grained lustrous satin nickel deposit, by incorporating in these baths certain quantities or concentrations of certain finely divided bath insoluble compounds, and plating while these pow dered mat erials are maintained in agitation in these baths.

The method .of the invention also includes the step-of removing from the plated surface any excess powdery material clinging to the plate prior to additional treating steps, such as the preferred final stepof chromium plating.

'The class of bath insoluble fine powders which when added to "agitated bright nickelor semi-bright nickel platingbaths in concentrations from 10 to 500 grams per liter produce a pleasing fine-grained lustrous satin nickel directly from the bath, is the sulfates, carbonates, phosphates and oxalates of the alkaline earth metals, barium, strontium and calcium. Not all of the compounds produce exactly equal effects, for example barium sulfate is superior to calcium oxalate. All of the carbonates are aboutequal, though barium carbonate and strontium carbonates are easier to use because they cause less caking problems. However, barium carbonate, as well as phosphate and oxalate are toxic powders. For this reason, barium sulfate is preferred over the other mentioned barium compounds, because it is'not toxic. Barium chromate fine powderdid not give, rise to the satin nickel plate, and in high concentrations actually stopped the nickelplating. Since the carbonate powders of calcium, strontium and barium will react with acid they tend to neutralize the nicketb'ath to pH values of .Ofto 6.0 and partially form insoluble sulfates of these metals as well as some, insoluble nickel hydroxide and carbonate In fact, fine I 3,152,973 Patented Oct. 13, 1964 nickel carbonate powder or basic nickel carbonate powder can be used to raise the pH of'the nickel bath to 5.0 to 5.2 before adding barium carbonate. It was also found that comparatively fine particle size nickel carbonate or basicnickel carbonate powder by itself at bath pH values of about 5.0 to 6.0 also produced the fine-grained lustrous v satin finish when present in concentrations of to 500 grams per liter in agitated bright nickel or semi-bright nickel baths.

Especiallydesirable results from a decorative as well as a corrosion resistant standpoint are obtained by the addition of very fine powders of barium sulfate, strontium sulfate, or calcium carbonate in concentrations of about 30 to 200 grams per liter to air-agitated bright nickel plating baths such as those described in US. 2,647,866, issued August 4, 1953; 2,800,440 and 2,800,442, issued July 23, 1957. Superfine barium sulfate powder is especially outstanding in performance. The nickel plate obtained from these agitated bright plating baths containing, for example, about 150 grams per liter of superfine barium sulfate powder, has a semi-bright microscopically-fine pitted surface with a satin smooth sheen of very pleasing appearance. The fine suspended powders such as those of calcium carbonate, strontium sulfate, barium sulfate, tend to cling to the nickel plate, and this effect and the specific physical structure, particle size and shape, amorphous texture, etc., and the chemical structure of the powder apparently causes the microscopically-fine pitting effect which converts the normally bright or semi-bright surface to a satin smooth sheen. The uniformity of the sheen is unusual and especially noteworthy in that a 0.2 mil to a 2 mil thick or thicker plate can have the same satin appearance. Thus, when contoured articles such as camera parts, ornaments, grilles, automobile dashboards, door handles, marine hardware, etc., are plated, the satin appearance of the plate in the recessed areas or low current density areas is the same as the plate in the higher current density areas.

Concentrations of fine barium sulfate powder as high as 500 grams per liter in the bath do not produce any appreciably different results than the optimum concentrations of about 50 to 200 grams per liter of superfine barium sulfate powder. Air agitation or mechanical agitation including ultra-sonic agitation of the baths can be used. The faster or more powerful the agitation and the finer the particle size down to colloidal dimensions, the lower the concentration of fine powder that is necessary, and concentrations as low as 10 grams per liter may be used to obtain a smoky satin finish by using strong agitation and powders having a size of about 0.1 to 0.3 micron or ultrafine particles having a size of 0.03 to 0.04 micron. Agitation is necessary to keep the fine powder suspended in the bath during plating. In general, however, it is preferred to use from about 50 to 200 grams per liter of very fine powder having a size less than 5 microns and preferably less than 2 microns in air-agitated baths.

Analysis of a satin nickel plate from an air agitated bright nickel bath containing superfine barium sulfate in a concentration of about 20O grams per liter shows up to about 2.5% barium sulfate uniformly distributed in the nickel plate. Microscopic examination of the surface of the plate shows an extremely uniform finely pitted surface. This satin plate has excellent adhesion, for example, to ferrous, copper, and brass surfaces just as the plate from the clear nickel bath, and it is quite surprising that these agitated baths containing 100 to 200 grams per liter of superfine barium sulfate give exceptionally smooth to the touch satin plate even in 20 mil and thicker plates, and that practically no pitting occurs. The addition of these fine powders in the same concentrations, that is, 50 to 200 grams per liter of, for example,

barium sulfate to agitated plain dull nickel baths, such as the Watts bath, makes the dull nickel plate obtained even duller and more unsightly in appearance.

The throwing power and covering power of the agitated bright nickel baths withfthe suspended powders is about the same as without the fine powders present. It was found that in plating articles with recessed areas and with shelf areas that no roughness was obtained on the areas on which settling can occur and this was quite unexpected particularly with the high density powders such obtained where brush or polishing lines are desired in a satin finish, by using coarse polishing grit such as 120 emery on the basis metal The original coarse polishing lines are diminished by the high levelingsatin nickel plate of this invention and though diminished are still visible. In this way, a highly corrosion resistant scratch brush finish satin nickel is obtained without having to resort to scratch brushing a final nickel plate and thus decreasing its corrosion protection.

When concentrations of less than about grams per liter of the ultra-fine powdersjof about 0.02 to 0.04 micron particle'size are used in agitated bright or semibright nickelplating baths, then the satin appearance of the nickel plate decreases, and the plate has a more smoky appearance, and has more reflectivity, especially in recessed areas. "In'general, it is preferred to use concentrations of the fine powders of 0.02 to 0.5 micron particle size greater than 10 grams per liter, with optimum results usually achieved with about 30 to 200 grams per liter. t

The carbonates of barium, strontium and calcium also form to a certain extent the insoluble sulfates when they react with the acidity of the Watts nickel bath. Thus, a mixed insoluble powder is formed, and this in some cases changes somewhat the texture of the satin finish obtained. For example, fine calcium carbonate powder (50-150 grams/liter) produces a smoky satin finish when added to an agitated all chloride bright nickel bath, and if. nickel or sodium sulfate is then added the satin texture is improved. Thus, with this particular fine powder, bright nickel baths of the Watts type or those containing some sulfate ions are preferred over the all chloride type. With fine barium sulfate powder this difference due to the type of bright nickel bath used was not noticeable, and in general, bright or semi-bright nickel plating baths of the Watts, high chloride, sulfamate and fluoborate baths ormixtures can be used. Also, other buffers besides boric acid may be used, such as'formates, citrates, etc. T

The use of dispersing agents, peptizing agents in conjunction with the fine powders is often helpful, especially with some powders such as calcium sulfate which tend to cake. It is also helpf'ul'to process the dispersion with high energy dispersion machines such as the Cowles Dissolver which accomplishes practically complete dispersion into ultimate particle size but while helpful, this treatment is not necessary, for obtaining excellent satin nickel plate. Such procedures help in reducing the need for usingthe higher concentrations of powder in the bath such as the to 200'grams per liter concentrations. However, concentrations of 100 to200 grams per-liter of a commercial fine powder such as Merck U.S.P. X-ray grade barium sulfate gives excellent satin" nickel plate when used as purchased in regular air agitated bright nickel "platingbalhs. There'are no particular operating troubles because concentrations of 150 grams per liter or higher of this powder are used in the bath instead of, for example, 40 to 50grams per liter of 0.1 to 0.35 micron particle size. The powders of extremely fine or ultra fine'particle size of 0.03 to 0.04 micron or less, are generally more expensive, that is, if. the great percentage of the particles are of these ultra-fine diameters, however, lower concentration can be usedtoobtain equivalent effects. Before technical grade powders are used commercially they should always be checked first in small scale testssuch as 1-4 liter baths before being added to large baths because certain harmful impurities such as metallic powders or too coarse particles may be present which will cause rough plate, especially on shelf areas. Except for the necessity of this precautionary check, technical grade fine powders normally produce equal results to those obtained from the use of high purity grades of the same particle size-and structure.

It is important to avoid metallic powders in these baths, for example, poorly cast nickel anodes which might powder during use and disperse nickel particles in the bath definitely can cause roughness, also high concentrations of activated carbon in the bath can cause very undesirable roughness. The carbon from rolled orcast carboncontaining nickel anodes, however, does not usually cause roughness when floating in the baths. High concentrations of iron dissolved as ferrous orferric iron in the baths do not cause settling roughness or gross pitting effects in the baths at the pH values of 3.8 to 5.5 although at such pH values dissolved iron tends to precipitate. Zinc or cadmium ions can be present in the baths in concentrations as high as about one gram per liter without detrimentally affecting the plate. Cadmium tends to whiten the plate somewhat. Copper carbonate is surprisingly not harmful inhigh concentrations. The presence of sodium and magnesium salts are not harmful. Ammonium salts in concentrations higher than about 15 grains per liter is in general not desirable because of reduction of the limiting. cathode current density.

The pH of the baths may be from about 2 to 6,

though the preferred pH values are from about 3.5 to

5.2. In case of calcium, barium or strontium carbonate, the pH isautomatically raised to about 5.2 andeven to about 5.5. The pH of the baths can be raised with nickel carbonate powder, preferably finely precipitated powder, and the nickel carbonate powder can be left in the bath in high'concentration. The temperature of the baths can be from room to at least 170 F., though in general a temperature of about F. to about F. is preferred. Barium sulfate fine powder produced the best satin finish from the agitatedbright and semi-bright nickel plating baths. Barium carbonate, strontium sulfate and carbonate are next in order of preference. As already mentioned, the use of these fine powders of bariumsulfate or calcium carbonate, etc., does not create a satin sheen nickel plate when added to plain nickel baths that normally produce dull nickel deposits such as the Watts nickel bath. The nickel "bath must be a semi-bright or bright nickel plating bath.

sulfonicacids, naphthalene sulfonic acids, p-toluene sulfonamide, benzene sulfonamide, o-benzoyl sulfimide, allyl. sulfonic acid, 2-butyne-l,4 disulfonic acid, o-sulfobenzaldehyde, etc.; the addition agents which produce semibright sulfur free nickel plate such as formaldehyde, chloral hydrate, bromal hydrate, coumarin, butyne diol, used alone or in combinations; combinations of the sulfurthose of the organic sulfontype, and combinations of the latter with small concentrations of amines, such as quinaldine or unsaturated compounds such as N-allyl isoquinolinum bromide and other unsaturatde compounds, polyamines, etc. Cobalt and iron can be present in the nickel bath as the cobalt or ferrous sulfates, chlorides, sulfamates or fluoborates in concentrations as high as at least 40 grams per liter, yielding nickel alloy plates containing concentrations of cobalt and /or iron as high as 50%.

Surface active agents may be present in the baths, but are not usually necessary in the air agitated baths.

The maximum increase in satin sheen is obtained when the fine powders are used in the agitated full, bright nickel plating baths such as the air-agitated bright nickel in t plating baths possessing good levelingas those illustrated in Examples 1,2 and below. Less satin lustre, for example, that of Example 3, is obtained when the nickel baths contain only the carrier type brightener such as benzene sulfonic acids, naphthalene sulfonic acids, p-toluene sulfonamide, benzene sulfonamide, o-benzoyl sulfimide, etc. In. the latter cases the satin lustre is flatter. This is also true when the semi-bright sulfur-free type of addition agent such as formaldehyde, chloral hydrate or brornal, is used solely with the fine powders, and with these sulfurfree semi-bright addition agents suchas those mentioned,

as well as coumarin, it. is best to use the ultra-fine particle size powders of less than 0.2 micron particle size, and preferably less than 0.05 micron particle size as determined with the electron microscope. There seems to be a definite improvementin leveling with the semi-bright sulfur-free addition agents when these ultra-fine particle size powders are used. The corrosion protection to steel, aluminum,

magnesium, and zinc base die-castings of such'chromium plated nickel is greatly improved as shown by repeated passage of such severe accelerated tests as the Corrodkote,

,with and without a final, sulfur-containing bright nickel over-lay plate to give a double layered plate, so-called duplex or dual nickel, of 40 to 60 ratio to 80 to 20 ratio of ultra-fine satin semi-bright sulfur-free nickel to fully bright nickel. Furthermore, it was found that the satin nickel plate obtained from the agitated bright nickel plating baths containing organic sulfon-type addition agents and the fine powders asillustrated in Examples 1, 2 and 3 when plated to a thickness of l to 1.5 mils on steel or copper.plated zinc die-cast and given .the usual 0.01 mil final chromium will itself pass many successive Corrodkote and Cass test's of 20 hours each without any failure. This is due mainly'to the development of a very, fine favorable porosity pattern in the final thin, 0.01 mil,

chromium plate. If the fine'powder of barium sulfate or calcium carbonate, for example, is omitted, the resulting full bright nickel plate of the same thickness and with the samethin final'chromium plate will fail in only one cycle of 20 hours Corrodkote testing.

There is a strong tendency for the finely-divided powders, especially barium sulfate andcalcium carbonate to remain clinging to the nickel surface, after the plated article is withdrawn from the bath and rinsed thoroughly, and remains clinging even after the usual final chromium plate of 0.005 to 0.05mil is applied. In the case of calcium carbonate, the chromic acidof the chromium plating bath attacks the. clinging particles on the nickel plate and causes tiny spots in the. chromium plate; barium tsequeste ring agents, it was found that a very thin plate from a zinc cyanide bath, for example, about 1 to 3 minutes plating followed by an'acid or alkaline dip toremove the zinc, also removed the tightly clinging barium sulfate particles. Actually, theparticles on the work look like a fine dust or talc and are not really too unsightly even if left on, and-they do not hurt the chromium plate; They are readily wiped off with a cloth, or can be removed to a certain extent by ultra-sonic cleaning.

The satin nickel plate accepts chromium plate like regular nickel plate, and in general only the usual thicknesses of final chromium need be used, that is, 0.01 mil, though thicknesses of 0.1 mil or 0.2 mil may be used. Besides, the final satin nickel finish as such, or with the usual final chromium finish, the satin nickel plate can be given a rhodium, silver, tin, brass, bronze, copper, gold, or tin-nickel (65-35) alloy or other final thin coating. Thin wax, or soluble-wax, films or clear lacquers greatly decrease finger marking of the final coatings, such as nickel, bronze, silver, brass, etc. Chromium, rhodium, and tin-nickel alloy plate do not need these organic coatings.

In general, for indoor use, satin nickel coatings of only 0.2 to 0.5 mil thickness are needed. For outdoor exposure in industrial or marine atmospheres thicknesses of 1 to 1.5 mils should be used. Also, the satin nickel can be used as the top layer of a double layered or duplex nickel coating, with the undercoat consisting of at least 0.7 mil of semi-bright sulfur freenickel. This would be for the most severe outdoor exposure as for marine hard ware. As already mentioned, however, the corrosion protection to steel, aluminum, magnesium, brass and zinc of the satin nickel with the usual final chromium plate (0.01

- the production of the satin nickel plate of this invention.

Especially excellent results are produced by Examples 1 to 5. In general, the cathode current density is from about 10 to at least 100 amps/sq. ft. Barium and strontium sulfate powder is preferred over calcium sulfate; and barium and strontium carbonate over calcium carbonate, mainly because of the excessivecaking tendency of these calcium compounds in the absence of agitation, e.g., when the bath is not in use. For this reason, mechanical agitation is preferred for these calcium compounds insteadof air agitation. When the agitation is turned off, the fine powders settle and the clear nickel solution can be subjected to ordinary filtration treatments'. The settled powders can readily be removed by a slurry pump for any re-processing or milling if it is desired. Also, it is possible to filter with traveling screens to screen out the coarser powders. In general, precipitated-powders are preferred because of their very fine size, though any process for fine powder manufacture which produces the powder in clean form and with a high percentage of the powder less than about 2 micron particle size, and preferably of 0.02 to 0.5 micron particle size will accomplish the result. Powders containing large quantities of particles having diameters greater than about 5 microns tendto produce rougher plate and for most applications are preferably avoided. Mixtures of powders may be used such asbarium sulfate and carbonate, barium sulfate and nickel carbonate, strontium sulfate and barium sulfate, barium carbonate, calcium carbonate and barium sulfate, etc. Comparable particle size fluorides'of calcium, strontium and barium are also useful in about the same proportions and under similar conditions as the sulfates, carbonates, phosphates and oxalates described above in detail.

The satin nickel plate of this inventionhas about 10 million to about 50 million' micro-pits per square inch,

as determined by microscopic evaluation'at 250x magnification, and inall cases the plate contains a sufiicient 1 Example I i 1 Conc. grams/ liter BaSO fine powder (0.1 to 0.3 micron particle size) 7'5-150 NiSO .6H O 150-300 NiCl .6H O 30-100 H 80 30-40 p-Toluene sulfonamide 1-2 o-Benzoyl sulfimide 0.1-2 Allyl sulfonic acid 0.5-6 N-allyl quinaldinium bromide 0.002-0.0l pH=3.0-5.2. Temp.= room to 160F. Air agitation of the bath.

Example II Conc.

grams/ liter BaSO fine powder (0.03-0.3 micron particle size) 40-200 NiSO .6H Y 150-300 MCI- .611 0 30-150 H BO 30-40 o-Benzoyl sulfimide Y V 1-3 Allyl sulfonic acid 0.5-4 2-butyne-l,4-disulf0nic acid 0.1-10 2-butynoxy-l,4-diethane disulfonic acid 0.05-0.1 pH=2.8 to 5.2. i Temp.=room to 165 F. Air agitation.

Example III Cone.

' grams/liter BaSQ superfine powder 30-200 NiSO .6H O 75-200 NiCl' .6H O-' 30-150 H BO 4. -5 30-40 o-Benzoyl sulfimide 1-3 p-Toluene sulfonamide 1-2 pH=3.0 to 5.0. Temp.=room to 180 F.

Air agitation or mechanical or both.

Example IV Sr'CO or SrSO or BaCO or BaSO; ultra-fine powder or mixtures (0.03 to 0.04 micron) particle size conc. -200 NiSO .6H O 150-350 NiCl- .6H O 30-53 H BO 30-40 Chloral hydrate e 0.1 Formaldehyde 0.04

CHa oionr-k mocnr-czo-omou; ..u.04

pH=3.8-5.2 (for the carbonates pH=5.0-5.2). Temp.=room to 150 F.

Mechanical agitation for the carbonates, and mechanical or air-agitation for the sulfates.

- Example V BaCO ,"SrCO or CaCO ultrafine powder (0.03-0.04 micron) 10-50 NiSO .6H O 100-300 NiCl .6H O 30-75 H 30 30-40 Allyl sulfonic acid 1-3 Benzene sulforiamide 1-3 2-butynoxy-1,4-diethane disulfonic acid 0.1-0.2

Temp.:room to 160 F. Vigorous mechanical agitation.

8 Examplc VI BaSO or SrSO, microfine powder 50-200 NiSO .6H O -350 NiCl .6H O 30-75 H BO 30-40 Benzene sulfonamide 1-3 Allyl sulfonic acid 1-3 2' butyrioxy- 1,4 diethoxyethane disulfonic acid Q 0.l0.2

pH'=3.0-5.0. Temp. =roorn to 170 F. Air agitation.

Example VII Barium, strontium or calcium oxalate microfine powder (0.03 to 0.3 micron) cone. 10-200 -NiSO .6H O 100-300 NiCl .6H O 30-100 H BO 30-40 Ni(BF 1-3 o-Benzoyl sulfimide 0.2-3 p-Toluene sulfonamide l-Z Allyl sulfonic acid 1-4 2-butynoxy-l,4-diethane disulfonic acid 0.1-0.3 'pH=4.8 to 5.2.

Temp.=room to F. Mechanical agitation.

Example VIII Barium, strontium or calcium phosphate (barium phosphate preferred) microfine powder a 10-100 'NiCO microfine powder 5-75 NiSO .6H O 100-300 NiCl .6H O 30-60 H3BO3 p-Toluene sulfonamide 1-2 Allyl sulfonic acid 1-4 2-butynoxy-1,4-;diethane disulfonic acid 0.1-0.3 pH=5.0-5.2. Temp.=room to F. Mechanical agitation.

Example IX Nickel carbonate or basic nickel carbonate (less than 2 micron particle size) conc 30-150 Barium sulfate 0-100 NiSO .6H O 100-300 NiCl.6H O 30-150 H BO 30-40 Allyl sulfonic acid 0.5-3 p-Toluene sulfonamide 1-2 o-Benzoyl sulfimide 1-2 Z-butynoxy-l,4-diethoxyethane disulfonic acid" 0.1-2.2

What is claimed is: g

1. A method for electrodepositing a fine-grained lustrous plate which is essentially nickel comprising the step of electrolyzing with externally applied current an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel sulfate, nickel chloride, nickel fiuoborate, nickel sulfamate and mixtures of at least one said nickel salt with up to about 40 grams per liter of at least one salt selected from the group consisting of the sulfates, chlorides, fluoborates and sulfamatesof cobalt and iron and at least one soluble organic addition agent capable of producing said finegrained lustrous plate, said bath containing about 10m ,-about 500 grams per liter of at least one material selected from the group consisting of the sulfates, carbonates,

phosphates and oxalates of barium, strontium and cal- --,cium, said material being in the form of fine powder dispersed in said bath and having a particle size which is less than about microns average diameter, thereafter fine powder is barium sulfate.

3. A method in accordance with claim 1 wherein said fine powder is strontium sulfate.

4. A method in accordance with claim 1 wherein said fine powder is strontium carbonate.

5: A method in accordance with claim 1 wherein said fine powder is calcium oxalate.

. 6. A method for electrodepositing a fine-grained lustrous satin nickel plate. comprising the step of electroylzing an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel sulfate, nickel chloride, nickel fiuorborate, and nickel sulfamate and at least onesoluble organic addition agent capable of producing said fine-grained lustrous plate, said bath containing about 10 to about 500 grams per liter of nickel carbonate, and having a pH in the range of about 5.0 to about 6.0; said nickel carbonate being in the form of fine powder dispersed in said bath and having a particle size which is less than about 5 microns average diameter, and

, thereafter plating on said surface an overlayer of a metal selected from the group consisting of chromium, rhodium,

silver, tin, brass, bronze, copper, gold, and an alloy consisting of 65 tinand 35% nickel.

7. A method for electrodepositing a fine-grained lustrous nickel plate comprising the step of electrolyzing with an externally applied current an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel sulfate, nickel chloride, nickel fluoborate, and nickel sulfamate and at least one soluble organic nickel brightener selected from the class consisting of aromatic and unsaturated aliphatic sulfonic acids, sulfonamides and sulfonimides, said bath containing about 10 to about 500 grams per'liter of at least one material selected from the group consisting of the sulfates, carbonates, phosphates and oxalates of barium, strontium and calcium, said material being in the form of fine pow der dispersed in said bath and having a particle-size which is less than about 5 microns average diameter; and thereafter plating on said surface an ove'rlayer of a metal selected from the group consisting of chromium, rhodium, silver, tin, brass, bronze, copper, ,gold, and an alloy con sisting of 65 tinand 35 nickel.

8. A method in accordance with claim 7 wherein the metal of said overlayer is chromium.

- 9. A composite electroplate on a metal surface susceptible to atmospheric corrosion which comprises a nickel plate with a metallic over-lay, said nickel plate having been electrodeposit ed from an acidic nickel plating bath containing, dissolved therein at least one organic nickel brightener capable of producing semi-bright to fully bright nickel plate and having dispersed therein at least 7 one type of bath insoluble inorganic non-metallic particles', the average diameter of the individual particles thereof being less than about 5 microns, an electrodeposited over-lay plate of a metal selected from the group consisting of chromium, rhodium, silver, tin, brass,

bronze, copper, gold and an alloy consisting of tin and 35% nickel on said nickel plate said over-lay plate being less than about 5 microns in thickness, said typeof particles being selected from the group consisting of the sulfates, carbonates, phosphates, and oxalates of barium, strontium and calcium, and said particles'in said nickel bath being present in an amount sufficient to produce a fine porosity pattern in the said over-lay plate.

10. A composite electroplate in accordance with claim 9 wherein said nickel plate directly overlies an electrodeposit consisting essentially of nickel.

11. 'A composite electroplate in accordance with claim 9 wherein said bath insoluble non-metallic particles are present in the nickel bath in a concentration of at least about 10 grams per liter.

12. A composite electroplate in accordance with claim 9 wherein said dissolved organic nickel brightener is selected from the class consisting of aromatic and unsaturated aliphatic sulfonic acids, sulfonamides and sulfonimides.

1-3. A composite electroplate in accordance with claim 12 wherein said dissolved organic nickel brightener is o-benzoyl sulfimide.

14. A composite electroplate in accordance with claim 9 wherein said over-lay plate is chromium.

15. A composite electroplate in accordance with claim 9 wherein said nickel plate directly overlies an electrodeposit consisting'essentially of lustrous nickel and said over-lay plate is chromium.

16. A method in accordance with claim 1 wherein said overlayer is chromium.

17. A method in accordance with claim 1 wherein said material is dispersed in said bath during plating by air agitation.

18. A method in accordance with claim 7 wherein said material is dispersed in said bath during plating by air References Cited in the file of this patent UNITED STATES PATENTS 942,729 Kern Dec. 7, 1909 970,755 Rosenberg Sept. 20, 1910 1,163,911 Hall Dec. 14, 1915 2,119,304 Viers et al L. May 3, 1938 2,318,592 Cupery May 11, 1943 2,483,996 De Marinis Oct. 4, 1949 2,637,686 McKay May 5, 1953 2,658,839 Talmey et al Nov. 10, 1953 2,728,720 De Long Dec. 27, 1955 2,756,489 Morris July 31, 1956 2,767,464 Nack et a1. Oct. 23, 1956 2,849,353 Kardos Aug. 28, 1958 2,999,798 Eitel Sept. 12, 1961 3,041,254 Pedler et al. June 26, 1962 3,061,525 Grazen Oct. 30, 1962 FOREIGN PATENTS 444,464 Great Britain Mar. 29, 1936 

1. A METHOD FOR ELECTRODEPOSITING A FINE-GRAINED LUSTROUS PLATE WHICH IS ESSENTIALLY NICKEL COMPRISING THE STEP OF ELECTROLYZING WITH EXTERNALLY APPLIED CURRENT AN AQUEOUS ACIDIC SOLUTION OF AT LEAST ONE NICKEL SALT SELECTED FROM THE GROUP CONSISTING OF NICKEL SULFATE, NICKEL CHLORIDE, NICKEL FLUOBORATE, NICKEL SULFAMATE AND MIXTURES OF AT LEAST ONE SAID NICKEL SALT WITH UP TO ABOUT 40 GRAMS PER LITER OF AT LEAST ONE SALT SELECTED FROM THE GROUP CONSISTING OF THE SULFATES, CHLORIDES, FLUOBORATES AND SULFAMATES OF COBALT AND IRON AND AT LEAST ONE SOLUBLE ORGANIC ADDITION AGENT CAPABLE OF PRODUCING SAID FINEGRAINED LUSTROUS PLATE, SAID BATH CONTAINING ABOUT 10 TO ABOUT 500 GRAMS PER LITER OF AT LEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING OF THE SULFATES, CARBONATES, PHOSPHATES AND OXALALTES OF BARIUM, STRONTIUM AND CALCIUM, SAID MATERIAL BEING IN THE FORM OF FINE POWDER DISPERSED IN SAID BATH AND HAVING A PARTICLE SIZE WHICH IS LESS THAN ABOUT 5 MICRONS AVERAGE DIAMETER, THEREAFTER ELECTRODEPOSITING ON SAID LUSTROUS PLATE AN OVERLAYER OF A METAL SELECTED FROM THE GROUP CONSISTING OF CHROMIUM, RHODIUM, SILVER, TIN, BRASS, BRONZE, COPPER, GOLD AND AN ALLOY CONSISTING OF 65% TIN AND 35% NICKEL. 